“It depends” is the correct answer to almost any question in software engineering, but not really practical. In this chapter, we will explore what “it” depends on.

In Part I of the book, you learned domain-driven design tools for analyzing business domains and making strategic design decisions. In Part II, we explored tactical design patterns: the different ways to implement business logic, organize system architec‐ ture, and establish communication between a system’s components. This chapter bridges Parts I and II. You will learn heuristics for applying analysis tools to drive var‐ ious software design decisions: that is, (business) domain-driven (software) design.

But first, since this chapter is about design heuristics, let’s start by defining the term

heuristic.